1. Field of the Invention
This invention relates to sprinkler seals and more particularly to sprinkler seals in sprinklers having rotatable heads which are powered by the pressure of the water being used for irrigation.
2. Description of the Prior Art
Rotary head sprinklers, especially the impulse type step-by-step rotary sprinklers, have been used extensively in irrigation of agricultural fields such as orange groves, corn fields, and the like. In dry seasons these sprinklers may be used almost continuously to supply the moisture required for proper plant growth. Multiple sprinkler heads are frequently combined into large irrigation systems which are usually elevated above the crops to be irrigated. These irrigation systems are usually fed with river, lake, or well water which has been only coursely filtered to remove large objects. Quite often sand and other small particle matter is suspended in the irrigation water and transferred through the pipes to the sprinkler heads. The high pressure used in the sprinkler systems can easily force such particulate matter between the lower seal bearing surfaces of the rotating head sprinkler devices, thereby causing rapidly accelerated wearing characteristics of the bearing surfaces. When such rotary head sprinkler devices are manufactured of polymers or plastic material, this wear becomes even more untenable since the sprinkler heads cannot be replaced easily from their inaccessibly high mounting positions.
Previous inventors have attempted to shield the lower bearing seal which separates the spindle and swivel mechanisms, thereby permitting the use of ordinary flat washers. In U.S. Pat. No. 3,080,123, Erns uses a single washer which acts as a combined wear washer and seal. In U.S. Pat. Nos. 3,204,873 and 3,204,874, Senninger uses a single wear washer and a single seal which are both semi-shielded from the water flow. In U.S. Pat. No. 2,904,261, Johnson uses a single wear washer with two seals which are both semi-shielded from the water pressure. Other references include U.S. Pat. No. 2,869,925, Crow; U.S. Pat. No. 3,669,356, Senninger; U.S. Pat. No. 2,310,796, Lappin; U.S. Pat. No. 2,086,515, Evans; U.S. Pat. No. 1,501,718, Olschewski; U.S. Pat. No. 1,710,107, Orr; U.S. Pat. No. 2,256,737, Englehart; U.S. Pat. No. 2,110,112, Rippey; U.S. Pat. No. 2,792,256, Sinex; U.S. Pat. No. 3,033,469, Green; U.S. Pat. No. 3,043,552; Ryerson; U.S. Pat. No. 3,193,203, Crow; U.S. Pat. No. 2,993,649, Holz; U.S. Pat. No. 3,017,123, Rinkewich; and U.S. Pat. No. 2,878,062, Crow.